traffic engineering, effects of increasing capacity

traffic engineering, effects of increasing capacity

I think he was misinterpreting his findings. That looks to me like a classic substitution effect.

I must have explained it poorly, because that's just what he said. Except that he knows drivers also substitute trips at less convenient times and trip forbearance for a 30 mph freeway trip.

And his only point about the disparity between people claiming to hate driving 35 mph and what actually happens is that while they hate driving 35 mph, they like it enough to do it, which is all that matters. There are apparently enough people whose cutoff point of hating the freeway enough not to use it is right about 35 that adding new lanes doesn't significantly increase the speed.

I see the same thing in computers. Users accept performance that, to me, is maddeningly slow so that as computers get faster, application developers put in more features and keep it down at that speed.

Actually, I just remembered I quoted the wrong number. 35 mph is what he said yields the greatest freeway capacity, based on the following distance at which drivers feel comfortable at various speeds. I can't remember what the figure was for when people stop getting on the freeway. Probably 25. So as more people start using a 70 mph freeway, it absorbs the traffic and slows down steadily until it gets to 35, then crashes to 25 and the number of people getting on stabilizes there.